In mammals the principle oscillator of circadian rhythms or central clock is in the suprachiasmatic nucleus. This master oscillator is responsible for the sleep-wake cycle and hormonal rhythms (e.g. cortisol and melatonin). It is recognised that peripheral tissues such as immune cells and the liver also have clock genes and their own molecular oscillating ability. Daily rhythms in gene expression, physiology and behaviour persist under constant conditions and must, therefore, be driven by self-sustained biological oscillators called circadian clocks. Circadian clocks can count time only approximately and must be adjusted every day by the photoperiod in order to be in harmony with the outside world.
There is a desire to develop drug delivery means to provide controlled drug release in particular in accordance with the circadian rhythm of a patient. There are a number of conditions that would benefit from this treatment regimen, for example adrenal failure, primary, secondary tertiary adrenal insufficiency and steroid withdrawal, inflammatory diseases such as rheumatoid arthritis and in the treatment of depression and related depressive illnesses including chronic fatigue and myalgic encephalitis (ME).
Adrenal failure occurs in approximately 1/10,000 of the population. It may be due to either primary adrenal failure or secondary adrenal failure (which occurs due to pituitary failure which may be caused by a pituitary tumour or surgery). In primary adrenal failure, ACTH levels from the pituitary will be high and in secondary adrenal failure ACTH levels are inappropriately low. Administration of exogenous glucocorticoid or excessive secretion of endogenous glucocorticoid as in Cushing's syndrome results in suppression of the hypothalamo-pituitary adrenal (HPA) axis and occurs at all levels from the hypothalamus, pituitary and adrenal. This is referred to as tertiary adrenal insufficiency. This means that after excessive glucocorticoid exposure patients will have low cortisol levels and suffer from either a temporary or occasionally permanent cortisol deficiency (tertiary adrenal insufficiency) which results in fatigue, weight loss and a predisposition to an adrenal crisis.
Long acting potent synthetic glucocorticoids such prednisolone and dexamethasone are more likely to cause adrenal suppression than hydrocortisone. Hydrocortisone has the advantage of a short half-life (ca. 3 hours), is the native glucocorticoid, and can be given in low dose. However, current preparations of hydrocortisone cannot reproduce physiological rhythms of cortisol. To maximise the recovery of the HPA the glucocorticoid dose should not exceed the normal daily requirement and also allow initiation of the normal cortisol rhythm. If an immediate release glucocorticoid is given at night then it will generally prevent the night-time activation of the HPA axis. Suppression of the HPA axis may occur due to excessive treatment with exogenous glucocorticoids as in the treatment of inflammatory disorders such as rheumatoid arthritis and asthma. Similarly it is well recognised that Cushing's syndrome either due to a pituitary or ectopic tumour producing ACTH or an adrenal tumour producing cortisol can result in adrenal suppression.
Inflammation is a complex reaction of the body responding to damage of its cells and vascularised tissues. Inflammation can be acute or chronic. An acute inflammatory response is an immediate response by the immune system to a harmful agent. The response includes vascular dilatation, endothelial and neutrophil cell activation. An acute inflammatory response will either resolve or develop into chronic inflammation. Chronic inflammation is an inflammatory response of prolonged duration, weeks, months, or even indefinitely, whose extended time course is provoked by the persistence of the causative stimulus to inflammation within the tissue. The inflammatory process inevitably causes tissue damage. The exact nature, extent and time course of chronic inflammation is variable, and depends on a balance between the causative agent and the attempts of the body to remove it. Aetiological agents producing chronic inflammation include, but are not limited to: infectious organisms that can avoid or resist host defences and so persist in the tissue for a prolonged period; infectious organisms that are not innately resistant but persist in damaged regions where they are protected from host defences; irritant non-living foreign material that cannot be removed by enzymatic breakdown or phagocytosis; or where the stimuli is a “normal” tissue component, causing an auto-immune disease.
Glucocorticoids are commonly used for the treatment of inflammatory diseases. A common side-effect is suppression of the endogenous circadian rhythm of cortisol. The consequence is that patients may need weaning during withdrawal from glucocorticoids and during this weaning period they may have a flare of their disease or suffer from temporary cortisol deficiency that may provoke a flare in their disease. Suppression results from the provision of exogenous glucocorticoid that acts to suppress the circadian rhythm of cortisol. This suppression takes place at all levels of the hypothalamo-pituitary-adrenal axis. An alternative treatment regimen is the use of steroids to treat the inflammatory condition. A steroid such as prednisolone is used to treat rheumatoid arthritis and is effective at reducing inflammation. If steroids are used for extended periods their side effects include osteoporosis, thinning of skin, weight gain and muscle wasting all features of Cushing's syndrome. In addition the administration of steroids suppresses the endogenous circadian secretion of cortisol by the adrenal glands and this has consequences for the patient who is treated with the steroid.
It is well recognised that depression is associated with loss of the normal cortisol circadian rhythm. Similarly it is well recognised that Cushing's syndrome where a tumour results in loss of the circadian rhythm of cortisol causes depression [e.g. loss of circadian rhythm causes disease]. Conditions which result in depression or a general malaise are well known. These include, but are not limited to, clinical depression, reactive depression, post-natal depression, depression which results as a consequence of extensive surgery, chronic fatigue, myalgic encephalitis and conditions such as jetlag. Depressive conditions can also be induced by external effects which are self imposed, for example depression can result when a person is either dieting in an effort to lose weight or also when a person is attempting to treat an addiction, for example smoking or cocaine addiction. There are also less serious conditions which result in general malaise, for example shift workers who work unsociable hours can become tired and depressed due to disruption in their normal sleep pattern. It is also known that certain periods of the year induce depression, for example Christmas and Seasonal Affective Disorder (SAD). The physiological effects of depression are varied. However, some general characteristics include, hyperactivity of the hypothalamo-pituitary-adrenal axis resulting in high cortisol levels, loss of the cortisol circadian rhythm and sleep disturbance with early morning waking. High glucocorticoid levels at night-time or at the time of going to sleep may also themselves disturb sleep.
In WO2003/015793 and WO2010/032006 we disclose pharmaceutical delayed and sustained formulations that deliver glucocorticoids in a delayed and sustained fashion in the control of adrenal insufficiency and other conditions. This disclosure relates to the use of delayed release formulations which surprisingly can also be used in the treatment of conditions that would benefit from the circadian delivery of glucocorticoids such as hydrocortisone such as primary, secondary and tertiary adrenal insufficiency, inflammatory disease and conditions and depression and depressive illnesses